Conventionally, card readers for reading magnetic data recorded in a card and recording magnetic data into a card are widely used. In the industry of financial organizations and the like in which card readers are used, traditionally so-called “skimming” is a serious issue in which a criminal installs a magnetic head at a card insertion part of a card reader in order to fraudulently obtain magnetic data of the card by use of the magnetic head. Then, proposed is a card reader that generates a jamming magnetic field for prevention of reading a magnetic datum by use of a magnetic head for skimming (hereinafter, called a “skimming magnetic head”) (for example, refer to Patent Document 1). A card reader described in Patent Document 1 is provided with a jamming magnetic field generation mechanism that generates a jamming magnetic field. The jamming magnetic field generation mechanism includes a core formed of a magnetic material and an exciting coil wound around the core. Meanwhile, the jamming magnetic field generation mechanism is placed at a card insertion part where a card insertion slot is formed.
Furthermore, a card reader for dealing with a card, in which an IC chip is built and a magnetic stripe is formed, is traditionally well known (for example, refer to Patent Document 2). A card reader described in Patent Document 2 is provided with a metal sensor for detecting an external connection terminal of an IC chip, which is formed in a card. The metal sensor is provided with a core formed of a magnetic material, an exciting coil wound around the core, and a detecting coil. Meanwhile, the metal sensor is placed at a card insertion part where a card insertion slot is formed.